[Christine_J]

Question: How many g of 18O would you find in 1kg of standard ocean water?

Known info:
Density of sea water= 1025kg/m^3
The ratio of 18O to 16O in the modern ocean= 1:498.7 (18O is 2.005 ppt)

Attempt at a solution:
p=m/v v=(1kg)(1m^3/1025kg)=9.76*10^-4m^3 * 1000L/m^3 =0.98L

2.005ppt*1000ppm/1ppt = 2005ppm=2005mg/L * 0.98L = 1956.08mg *1g/1000mg =1.96g

[Borek]

I don't see a need to use water density. You are told 1:498.7 - I suppose that is mass/mass, so you need just a mass of oxygen in 1 kg of water.

However, question calls for standard sea water - which is not 100% water.